Gas turbine rotors may include several stages of rotor disks secured together with a stud (e.g. a bolt) and a nut. When spinning at high speed the weight of the nut results in a large amount of centrifugal force which must be reacted by the bolt threads. The centrifugal load can also impart an eccentricity between the bolt threads and the nut threads. Thus, the first engaging thread of the bolt, which bears most of the load in a standard nut and bolt configuration, experiences a circumferentially localized increase in load when spinning. If this effect is not, accounted for in the design of the nut and bolt it may reduce a life cycle of the nut and bolt arrangement.
Various attempts have been made to reduce the localized stress on the first engaging thread, many of which involve complicated manufacturing processes. Most of these are not specific to gas turbine engines. U.S. Pat. No. 8,038,377 to Ichiryu discloses a fastening device for a gas turbine engine rotor where the center of gravity of the nut is disposed in a nut hole (counterbore) and the nut is held concentric to the bolt to improve the axial and circumferential load distribution on the threads. However, in some configurations it is not possible to countersink the nut to this extent. Consequently, there remains room in the art for improvement.